scholarly journals Updating Subsurface Image of Khashim Al-Ahmer Gas Field Using the Interpretation for Anisotropic Velocity Model North-Eastern Iraq

2021 ◽  
Vol 54 (2F) ◽  
pp. 110-119
Author(s):  
Yasir Shyaa ◽  
Ali Al-Rahim
Keyword(s):  
Thick Layer ◽  
Seismic Energy ◽  
Velocity Model ◽  
Thrust Fault ◽  
Gas Content ◽  
Seismic Wave Velocity ◽  
Gas Field ◽  
High Attenuation ◽  
North Eastern ◽  
Interval Velocities

This research deals with structural interpretation of Khashim Al-Ahmer Gas Field North-Eastern Iraq in Diyala Province, using the interpretation of inhomogeneous velocity data. The specific target in this field is the gaseous Jeribe reservoir representing the L. Miocene-Tertiary period. A very thick layer of evaporates Al-Fatha Formation is overlap the Jeribe Formation in the gas field and play as a sealed bed and transition zone for faults movement as a thrust fault. The thrust fault with gas content negatively affected the seismic energy, causing a high attenuation below the level of Al-Fatha Formation in the dome of the Khashm Al-Ahmer structure. Using the interval velocities derived from the sonic logs of five surrounding wells that represent the inhomogeneous behavior of the seismic wave velocity within the rock layers, a model of the velocity behavior in the field was built and the extent of the Jeribe gas reservoir was reconstructed according to the new velocities interpretation data.

Case study: The importance of gas leakage in interpreting amplitude‐versus‐offset (AVO) analysis

Geophysics ◽  
1991 ◽  
Vol 56 (11) ◽  
pp. 1886-1895 ◽  
Author(s):  
M. K. Sengupta ◽  
C. A. Rendleman
Keyword(s):  
Seismic Energy ◽  
Gas Content ◽  
Bright Spot ◽  
Seismic Section ◽  
Gas Leakage ◽  
Hydrocarbon Reservoir ◽  
Reflection Amplitude ◽  
Amplitude Versus Offset ◽  
Amplitude Anomaly ◽  
Amplitude Versus

The amplitude‐versus‐offset (AVO) method has been shown to indicate the presence of gas sands if the reflection amplitude from the seal/reservoir‐sand interface, measured in a common midpoint (CMP) gather, increases rapidly with increasing shot‐to‐geophone distance (or offset). However, in a few instances, it has been observed that the seismic reflection amplitude does not increase with offset and may even decrease if there is widespread gas leakage above the hydrocarbon reservoir causing partial gas saturation in the overburden sediments. Gas‐charged sediments are known to attenuate seismic energy. Depending on the size and shape of this gas leakage zone, there may be higher attenuation of seismic amplitudes with increasing offset. We present one such case that involves a prominent “bright‐spot” amplitude anomaly corresponding to a 56‐ft‐thick (17 m‐thick) gas sand in the Gulf of Mexico slope. The reflection amplitude for the sand top was found to decrease with increasing offset. There is also evidence of gas leakage into the sediments above the reservoir. Color amplitude displays of the seismic section show a low‐amplitude diffused zone above the bright‐spot amplitude anomaly, which suggests gas leakage. Further evidence of gas leakage can be inferred from the significant gas content (including heavier hydrocarbons) observed in the mud log. Gas leakage is also confirmed by gather modeling in which the effects of leakage‐caused attenuation are accounted for in matching the variation of seismic amplitude with offset.

scholarly journals An integrated shear-wave velocity model for the Groningen gas field, The Netherlands

2017 ◽  
Vol 15 (9) ◽  
pp. 3555-3580 ◽  
Author(s):  
Pauline P. Kruiver ◽  
Ewoud van Dedem ◽  
Remco Romijn ◽  
Ger de Lange ◽  
Mandy Korff ◽  
...  
Keyword(s):  
The Netherlands ◽  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Velocity Model ◽  
Gas Field ◽  
Groningen Gas Field

scholarly journals A study of sub-basalt depth imaging using the local Radon attributes on the Erlend Tertiary volcanic complex - North of Shetland, UK

2008 ◽  
Vol 87 (2) ◽  
pp. 135-149
Author(s):  
A. Droujinine ◽  
J. Pajchel ◽  
K. Hitchen
Keyword(s):  
Model Building ◽  
Region Of Interest ◽  
Thick Layer ◽  
Velocity Model ◽  
Volcanic Complex ◽  
Depth Imaging ◽  
The North ◽  
Discrete Radon Transform ◽  
Imaging Results ◽  
And Migration

AbstractAcquiring conventional 3 km towed streamer data along a 2D profile in the North of Shetland (UK) enables us to use the local Radon-attributes within the context of depth processing methodology for accurate delineation of volcanic units and imaging beneath high-velocity layers. The objective is to map the radially-dipping structure of the Erlend pluton and to investigate the potential existence of relatively soft Cretaceous sediments underneath volcanic units. Success in the Erlend Volcano study requires strict attention to the separation between different groups of events. The crucial point is the generalized discrete Radon transform formulated in terms of local wavefront (dip and curvature) characteristics. This transform is utilized during pre-CMP processing and migration to minimize event-coupling artefacts. These artefacts represent cross-talk energy between various wave modes and include the unwanted part of the wavefield. We show how to produce detailed subsurface images within the region of interest (exploration prospect only) by applying the closely tied processes of prestack event enhancement and separation, well-driven time processing for velocity model building, and final event-based prestack depth imaging. Results show enhanced structural detail and good continuity of principal volcanic units and deeper reflections, suggesting a faulted 0.6 – 0.9 km thick layer of Cretaceous sediments in the proximity of well 209/09-1. Our interpretation complements existing low-resolution geophysical models inferred from gravity and wide-angle seismic data alone.

Influence of Dust Emission on Xi’an Atmospheric Organochlorine Pesticide Pollution

2012 ◽  
Vol 246-247 ◽  
pp. 576-580 ◽  
Author(s):  
Bian Hong Zhou ◽  
Cheng Zhong Zhang ◽  
Jian Hua Gao
Keyword(s):  
Soil Acidity ◽  
Significant Positive Correlation ◽  
Organic Matter Content ◽  
Physical Nature ◽  
Matter Content ◽  
Gas Content ◽  
Gas Field ◽  
Positive Correlation ◽  
Pesticide Pollution ◽  
Observation Area

The four north-central Shaanxi OCPs observed surface concentration of farmland were analyzed via GC-MS and GC/ECD, respectively, Xi’an observation area 6.110 ng•g-1, Tongchuan observation area 0.817 ng•g-1, Yan’an observation area 3.018 ng•g-1, an observation area in Yulin 5.286 ng•g-1, respectively. Be observed over the same period in Xi’an concentration of OCPs in air 325.773 pg•m-3, where the concentration of particles OCPs 160.883 pg•m-3, the concentration of gaseous OCPs 164.890 pg•m-3.Xi’an urban air particles and gas field surface soil OCPs and the OCPs was correspondence between the basic components of content, indicating that much of Xi’an OCPs in the air of dust released from the soil. The results show that the observation area at the same time with different content of each component of different OCPs, DDTs maximum concentration, mainly in the form of p, p’-DDT, BHC, followed by HCHs, mainly in the form of β-HCH; air, gas-eous and OCPs There are two forms of particulate, HCHs gas content was significantly greater than the particulate phase, DDTs substances content of particles greater than the gas content; OCPs in soil content and the physical nature of the soil, HCB, Chlordane, TN+CN and soil organic matter Content showed a significant positive correlation, chlordane, endosulfan, EnSO4 and soil acidity was a significant positive correlation, HCHs, DDTs and soil acidity were some negative.

Understanding The Mesozoics Beyond Basalt: A Case Study Of Sub-Basalt Imaging

2020 ◽  
Author(s):  
S. Sengupta
Keyword(s):  
Signal To Noise Ratio ◽  
Seismic Energy ◽  
Flood Basalt ◽  
Velocity Model ◽  
Significant Loss ◽  
P Wave ◽  
Deccan Volcanic Province ◽  
Deccan Volcanism ◽  
Impedance Contrast

The Deccan Volcanic Province of India is considered as one of the largest basalts-covered regions in the world, formed due to extensive outpouring of basaltic lavas during Deccan volcanism (∼65 Ma). The sedimentary sequence below the flood basalt is mainly characterized by Mesozoic strata with a varying thickness of 1000 m to 2500 m. It is considered that requisite heat generation due to Deccan Trap volcanism soon after the Cretaceous sedimentation may have acted as a catalyst in hydrocarbon potential in this area (Vardhan et al. 2008). However, it is essentially unexplored because of the limitations of conventional marine streamer P-wave seismic acquisition in imaging the structures both intra-basalt and sub-basalt. The major challenges can be considered as follows: Strong reflections due to high impedance contrasts at the top (and bottom) of the basalts leading to significant loss of transmitted seismic energy; Scattering of energy due to large acoustic impedance contrast at top and bottom of the basalt; Generation of multiples, both surface-related and interbed, from the top and bottom of the basalt, and intra-basalt boundaries, masking genuine primary reflections at the pre-basasediments; Significant attenuation of seismic energy in the basaltic sequences due to its complex internal structure generally causing weak sub-basasignal; Low signal-to-noise ratio creating ambiguity in estimating accurate velocity model of subsurface. This case study demonstrates that, even with legacy marine streamer surveys, an appropriate workflow of combining suitable advanced technologies can help to overcome the long-standing challenges of sub-basalt imaging. The reprocessed data show clear uplift in the sub-basalt imaging and the inversion results validate the quality of the new data in relation to the well logs.

Hybrid Simulation of Near-Fault Ground Motion for a Potential Mw 7 Earthquake in Lebanon

2021 ◽  
Vol 111 (5) ◽  
pp. 2441-2462 ◽  
Author(s):  
Rosemary Fayjaloun ◽  
Mayssa Dabaghi ◽  
Cecile Cornou ◽  
Mathieu Causse ◽  
Yang Lu ◽  
...  
Keyword(s):  
Ground Motion ◽  
Velocity Structure ◽  
Ground Motions ◽  
Seismic Energy ◽  
Velocity Model ◽  
Historical Seismicity ◽  
Stochastic Simulations ◽  
Hybrid Technique ◽  
Rupture Directivity ◽  
Near Fault

ABSTRACT Lebanon is a densely populated country crossed by major faults. Historical seismicity shows the potential of earthquakes with magnitudes >7, but large earthquakes have never been instrumentally recorded in Lebanon. Here, we propose a method to simulate near-fault broadband ground motions for a potential Mw 7 earthquake on the Yammouneh fault (YF)—the largest branch of the Dead Sea Transform fault that bisects Lebanon from north to south. First, we performed the first 3D tomography study of Lebanon using ambient noise correlation, which showed that Lebanon could be approximated by a 1D velocity structure for low-frequency (LF) ground-motion simulation purposes. Second, we generated suites of kinematic rupture models on the YF, accounting for heterogeneity of the rupture process, and uncertainty of the rupture velocity and hypocenter location. The radiated seismic energy was next propagated in the inferred 1D velocity model to obtain suites of LF ground motions (<1 Hz) at four hypothetical near-fault seismic stations. These LF simulations included the main features of near-fault ground motions, such as the impulsive character of ground velocity due to the rupture directivity or fling-step effects (so-called pulse-like ground motions). Third, to obtain broadband ground motions (up to 10 Hz), we proposed a hybrid technique that combined the simulated LF ground motions with high-frequency (HF) stochastic simulations, which were empirically calibrated using a worldwide database of near-fault recordings. Contrary to other hybrid approaches, in which the LF and HF motions are generally computed independently, the characteristics of stochastic HF ground motions were conditioned on those of LF ground motions (namely on the characteristics of the velocity pulse, if it existed, or on the absence of a pulse). The simulated peak ground accelerations were in agreement with the ones reported in the Next Generation Attenuation-West2 (NGA-West2) database for similar magnitude and distances and with three NGA-West2 ground-motion prediction equations.

Advances in velocity model-building technology for subsalt imaging

Geophysics ◽  
2008 ◽  
Vol 73 (5) ◽  
pp. VE173-VE181 ◽  
Author(s):  
Bin Wang ◽  
Young Kim ◽  
Chuck Mason ◽  
Xiansong Zeng
Keyword(s):  
Model Building ◽  
Seismic Energy ◽  
Velocity Model ◽  
Hydrocarbon Exploration ◽  
Building Technology ◽  
Depth Processing ◽  
Velocity Model Building ◽  
Formidable Challenge ◽  
Subsalt Imaging

Seismic imaging of hydrocarbon accumulations below salt is a formidable challenge because complexly shaped salt bodies severely distort wavefronts or scatter seismic energy. We have highlighted some recent advances in building a velocity model for subsalt imaging. There are three main stages: suprasalt velocity determination, salt-model definition, and subsalt velocity update. Volumetric high-resolution tomography that incorporates high-velocity contrast boundaries is used to derive a good sediment velocity model before building a salt model. To facilitate integration of interpretation and depth processing, beam-based interactive imaging is used to refine the salt geometry. For subsalt velocity update, either subsalt tomography or subsalt scan-based techniques can be used, depending on the quality of subsalt reflections. There are concepts and techniques for attaining subsalt images suitable for hydrocarbon exploration beneath complexly shaped salt bodies.

Velocity analysis without picking

Geophysics ◽  
1989 ◽  
Vol 54 (2) ◽  
pp. 191-199 ◽  
Author(s):  
John L. Toldi
Keyword(s):  
Field Data ◽  
Velocity Model ◽  
Point Of View ◽  
Velocity Analysis ◽  
Lateral Variation ◽  
Data Set ◽  
Initial Interval ◽  
Analysis Algorithm ◽  
Interval Velocity ◽  
Interval Velocities

Conventionally, interval velocities are derived from picked stacking velocities. The velocity‐analysis algorithm proposed in this paper is also based on stacking velocities; however, it eliminates the conventional picking stage by always considering stacking velocities from the point of view of an interval‐velocity model. This view leads to a model‐based, automatic velocity‐analysis algorithm. The algorithm seeks to find an interval‐velocity model such that the stacking velocities calculated from that model give the most powerful stack. An additional penalty is incurred for models that differ in smoothness from an initial interval‐velocity model. The search for the best model is conducted by means of a conjugate‐gradient method. The connection between the interval‐velocity model and the stacking velocities plays an important role in the algorithm proposed in this paper. In the simplest case, stacking velocity is assumed to be equal to rms velocity. For the more general case, a linear theory is developed, connecting interval velocity and stacking velocity through the intermediary of traveltime. When applied to a field data set, the method produces an interval‐velocity model that explains the lateral variation in both stacking velocity and traveltime.

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